Big Ben is the most famous example of a turret clock.
Turret clocks is the technical name for any large exterior clock made to be seen by many people at the same time. They do not need to be in a clock tower. Examples are churches, town halls, libraries, parks and squares, supermarkets, banks, and are often seen hanging over pavements outside jewellers, and other commercial premises.
Whilst the public only sees the face and hands, behind the face is a mechanism which drives the hands. That mechanism can be a very old mechanical device, often hundreds of years old, or more modern electric motors.
Hands are are made of metal, often copper but sometimes other metals, to stop them swinging down to the 6 o'clock position, they have counterweights. Look at the hands and see if there are extensions opposite the hands, if so you are likely to have a modern clock with electric motors, if no extensions can be seen you could have a traditional mechanism with counterpoises behind the dial connected to bevel gears.
Turret clocks are often on quality buildings, old clocks and their clock towers could have cost up to one third of the entire cost of the building. They were not cheap, and should be looked after.